We have found that olfactory receptors of the tiger salamander are organized topographically according to their odor specificities so that there are different maps for different groups of odorants. Our aims are (1) to determine the extent to which these maps constitute a potential basis for odor quality discrimination; (2) to establish the relative similarities and dissimilarities of maps for different odors and; (3) to characterize the response spectra and site type composition of individual receptors within populations that show peak sensitivity for a given odorant; (4) to identify physicochemical parameters which best account for the observed findings at these different levels. To elucidate these problems we plan to extend, refine and develop the mapping of the olfactory epithelium for different odorants under conditions which exclude patterning due to differential sorption of odorant molecules on the nasal mucus (i.e. by use of a punctate stimulator). Both electro-olfactograms and multiunit activity from the epithelium will be recorded. We also plan to characterize the response spectra of single receptors lying within zones of peak sensitivity for a given odorant and to analyze all data in relation to physico-chemical parameters.